wpiutil: Add WebSocket implementation (#1186)

This is a RFC 6455 compliant implementation with both client and server support.

wpiutil/src/main/native/include/wpi/WebSocketServer.h

@@ -0,0 +1,147 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#ifndef WPIUTIL_WPI_WEBSOCKETSERVER_H_
+#define WPIUTIL_WPI_WEBSOCKETSERVER_H_
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "wpi/ArrayRef.h"
+#include "wpi/HttpParser.h"
+#include "wpi/Signal.h"
+#include "wpi/SmallString.h"
+#include "wpi/SmallVector.h"
+#include "wpi/StringRef.h"
+#include "wpi/WebSocket.h"
+
+namespace wpi {
+
+namespace uv {
+class Stream;
+}  // namespace uv
+
+/**
+ * WebSocket HTTP server helper.  Handles websocket-specific headers.  User
+ * must provide the HttpParser.
+ */
+class WebSocketServerHelper {
+ public:
+  /**
+   * Constructor.
+   * @param req HttpParser for request
+   */
+  explicit WebSocketServerHelper(HttpParser& req);
+
+  /**
+   * Get whether or not this was a websocket upgrade.
+   * Only valid during and after the upgrade event.
+   */
+  bool IsWebsocket() const { return m_websocket; }
+
+  /**
+   * Try to find a match to the list of sub-protocols provided by the client.
+   * The list is priority ordered, so the first match wins.
+   * Only valid during and after the upgrade event.
+   * @param protocols Acceptable protocols
+   * @return Pair; first item is true if a match was made, false if not.
+   *         Second item is the matched protocol if a match was made, otherwise
+   *         is empty.
+   */
+  std::pair<bool, StringRef> MatchProtocol(ArrayRef<StringRef> protocols);
+
+  /**
+   * Accept the upgrade.  Disconnect other readers (such as the HttpParser
+   * reader) before calling this.  See also WebSocket::CreateServer().
+   * @param stream Connection stream
+   * @param protocol The subprotocol to send to the client
+   */
+  std::shared_ptr<WebSocket> Accept(uv::Stream& stream,
+                                    StringRef protocol = StringRef{}) {
+    return WebSocket::CreateServer(stream, m_key, m_version, protocol);
+  }
+
+  bool IsUpgrade() const { return m_gotHost && m_websocket; }
+
+  /**
+   * Upgrade event.  Call Accept() to accept the upgrade.
+   */
+  sig::Signal<> upgrade;
+
+ private:
+  bool m_gotHost = false;
+  bool m_websocket = false;
+  SmallVector<std::string, 2> m_protocols;
+  SmallString<64> m_key;
+  SmallString<16> m_version;
+};
+
+/**
+ * Dedicated WebSocket server.
+ */
+class WebSocketServer : public std::enable_shared_from_this<WebSocketServer> {
+  struct private_init {};
+
+ public:
+  /**
+   * Server options.
+   */
+  struct ServerOptions {
+    /**
+     * Checker for URL.  Return true if URL should be accepted.  By default all
+     * URLs are accepted.
+     */
+    std::function<bool(StringRef)> checkUrl;
+
+    /**
+     * Checker for Host header.  Return true if Host should be accepted.  By
+     * default all hosts are accepted.
+     */
+    std::function<bool(StringRef)> checkHost;
+  };
+
+  /**
+   * Private constructor.
+   */
+  WebSocketServer(uv::Stream& stream, ArrayRef<StringRef> protocols,
+                  const ServerOptions& options, const private_init&);
+
+  /**
+   * Starts a dedicated WebSocket server on the provided connection.  The
+   * connection should be an accepted client stream.
+   * This also sets the stream user data to the socket server.
+   * A connected event is emitted when the connection is opened.
+   * @param stream Connection stream
+   * @param protocols Acceptable subprotocols
+   * @param options Handshake options
+   */
+  static std::shared_ptr<WebSocketServer> Create(
+      uv::Stream& stream, ArrayRef<StringRef> protocols = ArrayRef<StringRef>{},
+      const ServerOptions& options = ServerOptions{});
+
+  /**
+   * Connected event.  First parameter is the URL, second is the websocket.
+   */
+  sig::Signal<StringRef, WebSocket&> connected;
+
+ private:
+  uv::Stream& m_stream;
+  HttpParser m_req{HttpParser::kRequest};
+  WebSocketServerHelper m_helper;
+  SmallVector<std::string, 2> m_protocols;
+  ServerOptions m_options;
+  bool m_aborted = false;
+  sig::Connection m_headerConn;
+
+  void Abort(uint16_t code, StringRef reason);
+};
+
+}  // namespace wpi
+
+#endif  // WPIUTIL_WPI_WEBSOCKETSERVER_H_